Field of the Invention
The invention relates to an image display apparatus, and particularly relates to a projection apparatus.
Description of Related Art
In a general use, due to that a placing position and a placing angle of a projection apparatus do not right face to and parallel to a projection screen, a projection direction of the projection apparatus is probably not perpendicular to a horizontal direction or a vertical direction of the projection screen, which may influence display quality of a projection image to cause a keystone distortion of the projection image. In a conventional correction method, a camera module is used to capture the projection image for image analyzing, and then the projection image is corrected in a manual or automatic adjusting manner. However, such correction method generally requires to capture a plurality of projection images, so that a correction speed of the projection apparatus is very slow, and the correction process is liable to be influenced by an ambient environmental light to cause correction failure or a correction error. Therefore, the projection apparatus cannot provide good image quality.
The information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Further, the information disclosed in the Background section does not mean that one or more problems to be resolved by one or more embodiments of the invention was acknowledged by a person of ordinary skill in the art.